package com.example.utils;

import com.example.entity.User;
import io.jsonwebtoken.Claims;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;
import lombok.Data;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Component;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

@Data
@ConfigurationProperties(prefix = "jwt")
@Component
public class JwtUtils {
    //密钥
    private String secret;
    //过期时间（毫秒）
    private Long expiration;

    /**
     * 从数据声明生成令牌
     * @param claims 数据声明
     * @return 令牌
     */
    private String generateToken(Map<String, Object> claims) {
        Date expirationDate = new Date(System.currentTimeMillis() + expiration);
        return Jwts.builder().setClaims(claims)
                        .setExpiration(expirationDate)
                        .signWith(SignatureAlgorithm.HS512, secret).compact();
    }

    /**
     * 从令牌中获取数据声明
     * @param token 令牌
     * @return 数据声明
     */
    public Claims getClaimsFromToken(String token){
        Claims claims;
        try{
            claims = Jwts.parser()
                    .setSigningKey(secret)
                    .parseClaimsJws(token)
                    .getBody();
        }catch (Exception e){
            claims = null;
        }
        return claims;
    }

    /**
     * 生成令牌
     * @param userDetails 用户
     * @return 令牌
     */
    public String generateToken(UserDetails userDetails){
        Map<String,Object> claims = new HashMap<>(2);
        claims.put(Claims.SUBJECT,userDetails.getUsername());
        claims.put(Claims.ISSUED_AT,new Date());
        return generateToken(claims);
    }

    /**
     * 从令牌中获取用户名
     * @param token 令牌
     * @return 用户名
     */
    public String getUsernameFromToken(String token){
        String username;
        try{
            Claims claims = getClaimsFromToken(token);
            username = claims.getSubject();
        }catch (Exception e){
            username = null;
        }
        return username;
    }

    /**
     * 判断令牌是否过期
     * @param token 令牌
     * @return 是否过期
     */
    public Boolean isTokenExpired(String token){
        Claims claims = getClaimsFromToken(token);
        Date expiration = claims.getExpiration();
        return expiration.before(new Date());
    }

    /**
     * 刷新令牌
     * @param token 原令牌
     * @return 新令牌
     */
    public String refreshToken(String token){
        String refreshedToken;
        try{
            Claims claims = getClaimsFromToken(token);
            claims.put(Claims.ISSUED_AT,new Date());
            refreshedToken = generateToken(claims);
        }catch (Exception e){
            refreshedToken = null;
        }
        return refreshedToken;
    }

    /**
     * 验证令牌
     * @param token 令牌
     * @param userDetails 用户信息
     * @return 是否有效
     */
    public Boolean validateToken(String token,UserDetails userDetails){
        User user = (User) userDetails;
        String username = getUsernameFromToken(token);
        return (username.equals(user.getUsername()) && !isTokenExpired(token));
    }
}
